US20140037921A1 - Optical information recording medium and laminate for optical information recording medium - Google Patents

Optical information recording medium and laminate for optical information recording medium Download PDF

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Publication number
US20140037921A1
US20140037921A1 US13/947,639 US201313947639A US2014037921A1 US 20140037921 A1 US20140037921 A1 US 20140037921A1 US 201313947639 A US201313947639 A US 201313947639A US 2014037921 A1 US2014037921 A1 US 2014037921A1
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United States
Prior art keywords
layer
optical information
resin
recording medium
layers
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US13/947,639
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English (en)
Inventor
Yo Ota
Tetsuhiro Sakamoto
Shiori Tashiro
Koichi Yasuda
Hiroshi Uchiyama
Mitsuaki Oyamada
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Sony Corp
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Sony Corp
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Assigned to SONY CORPORATION reassignment SONY CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SAKAMOTO, TETSUHIRO, OYAMADA, MITSUAKI, TASHIRO, SHIORI, UCHIYAMA, HIROSHI, YASUDA, KOICHI, OTA, YO
Publication of US20140037921A1 publication Critical patent/US20140037921A1/en
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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/2403—Layers; Shape, structure or physical properties thereof
    • G11B7/24035—Recording layers
    • G11B7/24044—Recording layers for storing optical interference patterns, e.g. holograms; for storing data in three dimensions, e.g. volume storage
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/24—Record carriers characterised by shape, structure or physical properties, or by the selection of the material
    • G11B7/2403—Layers; Shape, structure or physical properties thereof
    • G11B7/24035—Recording layers
    • G11B7/24038—Multiple laminated recording layers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y10T428/24942—Structurally defined web or sheet [e.g., overall dimension, etc.] including components having same physical characteristic in differing degree

Definitions

  • the present application relates to an optical information recording medium and a laminate for use in an optical information recording medium. More specifically, it relates to an optical information recording medium on which a recording mark can be formed by radiating light thereto.
  • CD compact disc
  • DVD digital versatile disc
  • Blu-ray Disc® Blu-ray Disc
  • optical information recording media have been desired to have larger capacities in recent years.
  • One of optical information recording media which employ such a method is an optical information recording medium that employs a method of previously containing, in a recording layer, a recording material which foams when absorbing photons and of radiating a light beam to form a void serving as a recording mark (hereafter referred to as “the void recording method”) (for example, see Japanese Unexamined Patent Application Publication No. 2008-176902).
  • the void recording method forms a void as a recording mark as described above, it has to use very high laser power to record an information signal. For this reason, there has been proposed a method of forming a recording mark on any one of interfaces between laminated multiple resin layers to reduce laser power which has to be used to record an information signal (hereafter referred to as “the interface recording method”) (for example, see Japanese Unexamined Patent Application Publication No. 2011-86327).
  • an optical information recording medium and a laminate for use in an optical information recording medium that can suppress interference between regeneration light or recording light reflected from two or more adjacent interfaces without having to precisely control the thickness.
  • An optical information recording medium includes a plurality of laminated resin layers. At least one of interfaces between the resin layers has a refractive index which gradually changes in a thickness direction of the resin layers.
  • a laminate for use in an optical information recording medium includes a plurality of laminated resin layers. Interfaces between the resin layers are configured such that a recording mark can be formed thereon. At least one of the interfaces between the resin layers has a refractive index which gradually changes in a thickness direction of the resin layers.
  • the present application it is possible to suppress reflection of regeneration light or recording light from the interfaces having a refractive index which gradually changes in the thickness direction of the resin layers. As a result, it is possible to suppress interference between regeneration light or recording light caused by interface reflection without having to control the thickness of the resin layers.
  • FIG. 1 is a schematic sectional view showing one example configuration of an optical information recording medium according to a first embodiment of the present application
  • FIG. 2 is a schematic sectional view showing an example configuration of a bulk layer
  • FIGS. 3A to 3C are process diagrams showing an example of a method for manufacturing the optical information recording medium according to the first embodiment of the present application
  • FIGS. 4A to 4C are process diagrams showing an example of a method for manufacturing the optical information recording medium according to the first embodiment of the present application.
  • FIG. 5 is a schematic sectional view showing another example configuration of the optical information recording medium according to the first embodiment of the present application.
  • FIGS. 6A to 6C are process diagrams showing an example of a method for manufacturing an optical information recording medium according to a second embodiment of the present application.
  • FIG. 7 is a schematic diagram showing an example of a method for forming a bulk layer
  • FIG. 8 is a diagram showing a simulation model of Test Example 1
  • FIGS. 9A to 9C are diagrams showing simulation models of Test Examples 2-1 to 2-3;
  • FIGS. 10A to 10C are diagrams showing simulation models of Test Examples 3-1 to 3-3;
  • FIGS. 11A to 11C are diagrams showing simulation models of Test Examples 4-1 to 4-3;
  • FIGS. 12A to 12D are diagrams showing simulation models of Test Examples 5-1 to 5-4;
  • FIGS. 13A to 13D are graphs showing simulation models of Test Example 5-5;
  • FIGS. 14A to 14D are process diagrams showing an example of a method for manufacturing an optical information recording medium according to a third embodiment of the present application.
  • FIGS. 15A to 15C are process diagrams showing an example of the method for manufacturing the optical information recording medium according to the third embodiment of the present application.
  • First embodiment an example of an optical information recording medium for recording an information signal on an interface
  • Second embodiment an example of a manufacturing method using a roll-to-roll process
  • Third embodiment an example of a manufacturing method using ultraviolet radiation
  • FIG. 1 is a schematic sectional view showing an example configuration of an optical information recording medium according to the first embodiment of the present application.
  • an optical information recording medium 10 includes a bulk layer 1 , a selection reflective layer 2 disposed on the bulk layer 1 , and a cover layer 3 disposed on the selection reflective layer 2 .
  • the optical information recording medium 10 may be further provided with a substrate 4 on a surface thereof opposite to the cover layer 3 .
  • the optical information recording medium 10 as a whole is in the form of an appropriate disc and has an aperture for chucking in the center thereof (hereafter referred to as the center hole).
  • a laser beam is radiated to interfaces B in the bulk layer 1 from the surface thereof adjacent to the cover layer 3 to record or regenerate an information signal.
  • the surface on which a laser beam is incident will be referred to as the incident surface, and the surface opposite to the incident surface as the back surface.
  • the cover layer 3 , the selection reflective layer 2 , the bulk layer 1 , and the substrate 4 forming the optical information recording medium 10 will be described in turn.
  • the cover layer 3 may be made of any material as long as the material is transparent.
  • it may be made of an organic material, such as a transparent plastic material, or an inorganic material, such as glass.
  • a plastic material include existing polymeric materials.
  • the existing polymeric materials include polycarbonate (PC), acrylic resin (PMMA), cyclo olefin polymer (COP), triacetylcellulose (TAC), polyester (TPEE), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide (PI), polyamide(PA), aramid, polyethylene (PE), polyacrylate, polyether sulfone, polysulfone, polypropylene (PP), diacetyl cellulose, polyvinyl chloride, epoxy resins, urea resins, urethane resins, and melamine resins.
  • an inorganic material include quartz, sapphire, and glass.
  • the cover layer 3 is, for example, in the form of an appropriate disc having a center hole in the center thereof.
  • One principal surface of the cover layer 3 is, for example, a corrugated surface, and the selection reflective layer 2 is disposed on the corrugated surface.
  • the corrugated surface has guide grooves for guiding the recording or reproduction position. Examples of the overall shape of the guide grooves when seen from the principal surface of the optical information recording medium 10 include various shapes, such as a spiral and a concentric circle.
  • Examples of the guide grooves include continuous grooves, pit trains, and combinations thereof.
  • the guide grooves may be meandered.
  • the selection reflective layer 2 is disposed on the corrugated surface of the cover layer 3 .
  • recording light for recording a mark on the bulk layer 1 (a first laser beam), as well as servo light for obtaining a tracking error signal or focus error signal on the basis of the guide grooves of the cover layer 3 (a second laser beam) are radiated to the selection reflective layer 2 .
  • the selection reflective layer reflects or absorbs the recording light radiated, the amount of recording light which reaches the inside of the bulk layer 1 decreases, resulting in a reduction in the apparent recording sensitivity.
  • the selection reflective layer 2 is preferably a reflective layer having selection characteristics of reflecting servo light but transmitting almost all recording light.
  • recording light and servo light are, for example, laser beams of different wavelengths.
  • the selection reflective layer 2 include a selection reflective layer having wavelength selection characteristics of reflecting light in the same wavelength range as servo light but transmitting light (for example, recording light) in other wavelength ranges.
  • Examples of the selection reflective layer 2 having such wavelength selection characteristics include a multilayer film in which low-refractive-index layers and high-refractive-index layers, which have different refractive indexes, are alternately laminated.
  • Examples of low-refractive-index and high-refractive-index layers include dielectric layers.
  • Examples of the material of dielectric layers include silicon nitride, silicon oxide, tantalum oxide, titanium oxide, magnesium fluoride and zinc oxide.
  • the bulk layer 1 is a laminate in which multiple resin layers are laminated (a laminate for use in an optical information recording medium), and interfaces are formed between the resin layers.
  • the bulk layer 1 is configured such that an information mark can be formed on any one of the interfaces between the resin layers.
  • the adjacent resin layers have, for example, different refractive indexes.
  • At least one of the interfaces between the resin layers has a refractive index which gradually changes in the thickness direction of the resin layers. To reduce the reflectance of regeneration light or recording light and to increase the transmittance thereof, such changes in refractive index are preferably continuous changes and more preferably changes such that the refractive index of one of resin layers forming an interface is tilted toward the refractive index of the other resin layer.
  • one of interfaces forming a single set preferably has a refractive index which continuously changes in the thickness of the resin layers, while the other interface preferably has a refractive index which discontinuously changes in such a direction.
  • a recording mark is formed, for example, on an interface having a refractive index which changes discontinuously.
  • the bulk layer 1 is a laminate in which multiple resin layers 11 a and multiple resin layers 11 b are laminated (a laminate for use in an optical information recording medium).
  • An interface B 1 is formed between a resin layer 11 a and a resin layer 11 b which are laminated in this order, and an interface B 2 is formed between the resin layer 11 b and a resin layer 11 a which are laminated in this order.
  • the bulk layer 1 is configured such that an information mark can be formed, for example, on any interface B 1 .
  • Adjacent resin layers, 11 a and 11 b have, for example, different refractive indexes.
  • the interface B 1 has, for example, a refractive index which gradually changes in the thickness direction from the resin layer 11 a toward the resin layer 11 b .
  • the gradual changes in refractive index are preferably continuous changes and more preferably changes such that the refractive index of one, 11 a , of resin layers forming an interface is tilted toward the refractive index of the other resin layer, 11 b .
  • the width of the transition region in which the refractive index gradually changes, in the interface B 1 is preferably about 100 nm or more and about 1 ⁇ m or less.
  • the interfaces B 1 preferably have a refractive index which continuously changes in the thickness direction of the recording layers 11
  • the interfaces B 2 preferably has a refractive index which discontinuously changes in such a direction.
  • a recording mark is formed, for example, on any interface B 2 having a refractive index which changes discontinuously.
  • Two resin layers, 11 a and 11 b , forming an interface having a gradually changing refractive index are preferably mutually dissolved in the interface.
  • the “mutually dissolved” means that the material composition of the two resin layers, 11 a and 11 b , continuously changes in the transition region having a width of about 100 nm or more in the thickness direction from 11 a toward 11 b .
  • FIG. 2 is a sectional view showing an example configuration of the bulk layer.
  • the bulk layer 1 is a laminate in which multiple recording layers 11 a serving as first resin layers and intermediate layers 11 b serving as second resin layers are alternately laminated.
  • the bulk layer 1 has the multiple first interfaces B 1 and multiple second interfaces B 2 formed by the recording layers 11 a and intermediate layers 11 b .
  • a first interface B 1 is formed by a recording layer 11 a and an intermediate layer 11 b adjacent to the incident surface of the recording layer 11 a ;
  • a second interface B 2 is formed by the recording layer 11 a and an intermediate layer 11 b adjacent to the back surface of the recording layer 11 a .
  • One of the first interface B 1 and the second interface B 2 preferably has a continuously changing refractive index; the other interface preferably has a discontinuously changing refractive index.
  • the configuration of the first interface B 1 and the second interface B 2 is employed, a recording mark is formed, for example, on any interface having a discontinuously changing refractive index, of the first interfaces B 1 and the second interfaces B 2 .
  • the average thickness of the recording layers 11 a is preferably 30 nm or more and 5 ⁇ m or less, more preferably 30 nm or more and 1 ⁇ m or less.
  • the average thickness of the recording lights 11 a is 5 ⁇ m or less and in particular 1 ⁇ m or less, the effect of interference between light reflected from the interface B 1 adjacent to the incident surface of the recording layer 11 a and light reflected from the interface B 2 adjacent to the back surface thereof tends to be at a non-negligible level.
  • the effect of interference between light reflected from the interface B 1 adjacent to the incident surface of the recording layer 11 a and light reflected from the interface B 2 adjacent to the back surface thereof tends to be at a negligible level, that is, at a level such that the effect can be isolated as a focus error signal.
  • the thickness at which apparent reflected light is maximized by an optical enhancement effect caused by interference is about 80 nm at a refractive index n of 1.3 and about 55 nm at a refractive index n of 1.8.
  • the thickness of a thin film is smaller than 30 nm, which is about half the thickness when the refractive index n is 1.8, any optical interference between the front and back surfaces thereof does not have to be considered.
  • the lower limit of the average thickness of the recording layers 11 a is preferably set to 30 nm.
  • the average thickness of the recording layers 11 a refers to the average distance between the first interfaces B 1 and the second interfaces B 2 . If, in one of these interfaces, the materials of the recording layer 11 a and the intermediate layer 11 b forming that interface are mutually dissolved, the position of that interface is defined as follows. That is, if the composition of the material of the recording layer 11 a is represented by A and the composition of the material of the intermediate layer 11 b is represented by B, the position at which the composition B is averagely 90 mol % is defined as the position of that interface.
  • the materials of the recording layer 11 a and the intermediate layer 11 b are, for example, materials having different refractive indexes.
  • Examples of the materials of the recording layer 11 a and the intermediate layer 11 b include organic materials and organic-inorganic composite materials.
  • At least one of the recording layers 11 a and the intermediate layers 11 b may contain an additive, as necessary. If at least one of the recording layers 11 a and the intermediate layers 11 b contains an additive, the refractive index of the interfaces B 1 or interfaces B 2 may be gradually changed by changing the concentration of the additive in the interfaces B 1 or interfaces B 2 .
  • Examples of an organic material include at least one selected from the group consisting of a thermoplastic resin, a thermosetting resin, an energy beam-curable resin, and the like.
  • thermoplastic resin examples include aromatic polyesters, such as polyethylene terephthalate, polyethylene2,6-naphthalene, and polybutylene terephthalate, and polyolefins, such as polyethylene and polypropylene.
  • aromatic polyesters such as polyethylene terephthalate, polyethylene2,6-naphthalene, and polybutylene terephthalate
  • polyolefins such as polyethylene and polypropylene.
  • Alternatives include polyvinyls, such as polystyrene, polyamides, such as nylon66(poly(hexamethylenediamine-co-adipic acid)), and aromatic polycarbonates, such as bisphenol A polycarbonate.
  • Other alternatives include homopolymers, such as poly sulfone, resins containing a copolymer of homopolymers as a main ingredient, and fluororesins.
  • Yet other alternatives include mixtures of the resins exemplified.
  • thermosetting resin examples include phenol resins, melamine resins, urea resins, and epoxy resins.
  • epoxy-terminated resins are preferred in terms of flexibility (for example, optical design, light absorption function, or the like).
  • An energy beam-curable resin is a resin which can be cured by radiating an energy beam thereto.
  • the energy beam refers to an energy beam that can trigger polymerization reaction, such as radical polymerization, cation polymerization, or anion polymerization. Examples thereof include an electron beam, an ultraviolet ray, an infrared ray, a laser beam, a visible ray, ionizing radiation (x-ray, ⁇ -ray, ⁇ -ray, ⁇ -ray, etc.), a microwave, and a high-frequency wave.
  • An organic-inorganic composite material may be used as an energy beam-curable resin composition. Alternatively, a mixture of two or more energy beam-curable resin compositions may be used.
  • a preferred energy beam-curable resin composition is an ultraviolet-curable resin.
  • an ultraviolet-curable resin examples include compounds containing one or more (meta)acryloyl groups.
  • the (meta)acryloyl group refers to an acryloyl group or metaacryloyl group.
  • Specific examples of an ultraviolet-curable resin include an ultraviolet-curable resin formed by preparing any amount of monomer from the ARONIX series available from Toagosei Co., Ltd.
  • Examples of a monofunctional monomer of an ultraviolet-curable resin include isobutyl acrylate, t-butyl acrylate, iso-octyl acrylate, lauryl acrylate, stearyl acrylate, and the like available from Osaka Gas Chemicals Co., Ltd.
  • Examples of an organic-inorganic composite material include nanocomposites formed by combining an organic material and an inorganic material at a nano level.
  • the refractive index of the interface B 1 or interface B 2 may be gradually changed by a preparing a nanocomposite material composition.
  • An Information signal is recorded on the optical information recording medium 10 thus configured as follows. That is, when a recording layer 11 a absorbs a laser beam, it generates heat and becomes deformed (for example, thermally expands and becomes convex) using the heat. An adjacent intermediate layer 11 b then imitates the deformation, so that the interface between these layers deforms itself from a flat surface to a curved surface. Thus, a recording mark (phase pit) is formed.
  • the position in which recording is performed by focusing a laser beam is preferably a position which is slightly closer to the recording layer 11 a than the interface, but not limited to such a position.
  • the position in which recording is performed by focusing a laser beam may be a position which is slightly closer to the intermediate layer 11 b than the interface.
  • the cover layer 4 is, for example, in the form of an appropriate disc having a center hole in the center thereof.
  • the material of the substrate 4 may be any of a transparent material and an opaque material and may be, for example, a plastic material or glass.
  • a plastic material is preferred in terms of formability. Examples of a plastic material include polycarbonate resins, polyolefin resins, and acrylic resins. Polycarbonate resins are preferred in terms of cost.
  • FIGS. 3A to 3C there will be described an example of a method for manufacturing the optical information recording medium 10 according to the first embodiment of the present application.
  • a first resin composition 12 a is dropped on the inside radius of a substrate 4 using an applicator 21 a , and the first resin composition 12 a dropped is stretched in the circumferential direction of the substrate 4 by spin coat to form a coating having a uniform thickness on the substrate 4 .
  • the first resin composition 12 a include thermosetting resins and ultraviolet-curable resins.
  • the resin composition that can be used in the present manufacturing method is not limited to these and may be an energy beam-curable resin, thermoplastic resin, or the like other than ultraviolet-curable resins, as described above.
  • the coating formed on the substrate 4 is semi-cured by radiating an infrared ray or ultraviolet ray from a radiation source 22 a .
  • a semi-cured film 13 having a uniform thickness is formed on the substrate 4 .
  • the radiation source 22 a for infrared radiation include IR lamps
  • examples of the radiation source 22 a for ultraviolet radiation include UV lamps.
  • the coating can be semi-cured by adjusting the infrared radiation time or post-radiation wait time. If an ultraviolet-curable resin is used as the first resin composition 12 a , the coating can be semi-cured by adjusting the ultraviolet dose (the cumulative amount of light). The ultraviolet dose is preferably set to 80% or less of the dose when completely curing the coating.
  • a second resin composition 12 b is dropped on the inside radius of the substrate 4 using an applicator 21 b , and the second resin composition 12 b dropped is stretched in the circumferential direction of the substrate 4 by spin coat to form a coating having a uniform thickness on the semi-cured film 13 .
  • the second resin composition 12 b include thermosetting resins and ultraviolet-curable resins.
  • the resin composition that can be used in the present manufacturing method is not limited to these and may be an energy beam-curable resin, thermoplastic resin, or the like other than ultraviolet-curable resins, as described above.
  • the coating made of the second resin composition 12 b formed on the semi-cured film 13 , as well as the semi-cured film 13 made of the first resin composition 12 a are completely cured.
  • a recording layer 11 a and an intermediate layer 11 b are formed on the substrate 4 .
  • an interface B 1 having a gradually changing refractive index is formed between the first resin composition 12 a and the second resin composition 12 b .
  • the radiation source 22 b for infrared radiation include IR lamps
  • examples of the radiation source 22 B for ultraviolet radiation include UV lamps.
  • a cover layer 3 having a selection reflective layer 2 thereon is bonded to one principal surface of the bulk layer 1 formed on the substrate 4 .
  • the desired optical information recording medium 10 is obtained.
  • the first embodiment it is possible to suppress reflection of recording light or regeneration light from the interface B 1 having a refractive index which continuously changes in the thickness direction of the intermediate layer 11 b formed on the recording layer 11 a .
  • FIG. 5 is a schematic sectional view showing another example configuration of the optical information recording medium according to the first embodiment of the present application.
  • the optical information recording medium 10 may have a multilayer structure in which the selection reflective layer 2 , the bulk layer 1 , and the cover layer 3 are laminated on one principal surface of the substrate 4 in this order.
  • the principal surface of the substrate 4 is formed into a corrugated surface serving as guide grooves for guiding the recording position or regeneration position.
  • the selection reflective layer 2 reflects servo light efficiently and suppresses reflection of recording light.
  • a purpose for suppressing reflection of recording light is to prevent stray light reflected from the selection reflective layer 2 from affecting a recording operation.
  • Examples of the selection reflective layer 2 thus configured include the above multilayer film, in which the multiple low-refractive-index layers and multiple high-refractive-index layers are alternately laminated, as well as alloy thin films made of Ag, Cu, Au, or the like and thin films made of titanium nitride or the like.
  • FIGS. 6A to 6C there will be described an example of a method for manufacturing an optical information recording medium 10 according to a second embodiment of the present application.
  • a bulk layer 1 (a laminate for use in an optical information recording medium) in which multiple recording layers 11 a and multiple intermediate layers 11 b are alternately laminated.
  • the bulk layer 1 is formed, for example, by stamping a belt-shaped multilayer film (a laminate for use in an optical information recording medium) into a disc shape. Details of the method for forming the bulk layer 1 will be described later.
  • a cover layer 3 having a selection reflective layer 2 thereon is bonded to one principal surface of the bulk layer 1 via a bond.
  • a bond include photosensitive resins, such as ultraviolet-curable resins, and pressure-sensitive adhesives (PSAs).
  • a substrate 4 is bonded to the other principal surface of the bulk layer 1 via a bond, as necessary.
  • a bond include photosensitive resins, such as ultraviolet-curable resins, and pressure-sensitive adhesives.
  • a coating roll 41 a is partially immersed in a first resin composition 12 a reserved in a reservoir 44 a and then rotated to pull up the first resin composition 12 a with the surface of the coating roll 41 a .
  • an excess portion of the first resin composition 12 a pulled up with the surface of the coating roll 41 a is scraped off using a doctor blade 43 a .
  • a protective sheet 31 is interposed between a pressure roll 42 a and the coating roll 41 a and pressed against the coating roll 41 a by the pressure roll 42 a so that the first resin composition 12 a is uniformly transferred to the protective sheet 31 .
  • a uniform coating is formed on a surface of the protective sheet 31 .
  • Resin layers 11 a and 11 b forming the recording sheet have similar functions and materials to those of the above resin layers 11 a and 11 b used when forming a laminate by spin coat.
  • the semi-curing unit 45 a is, for example, a unit configured to radiate an ultraviolet ray or infrared ray. If the first resin composition is an ultraviolet-curable resin, the semi-curing unit 45 a may be, for example, a UV radiation unit. If the first resin composition is a thermosetting resin, the semi-curing unit 45 a may be, for example, a dryer (heater).
  • the coating can be semi-cured by adjusting the infrared radiation time and post-radiation wait time. If an ultraviolet-curable resin is used as the first resin composition 12 a , the coating can be semi-cured by adjusting the ultraviolet dose (the cumulative amount of light). The ultraviolet dose is preferably set to 80% or less of the dose when completely curing the coating.
  • a coating roll 41 b is partially immersed in a second resin composition 12 b reserved in a reservoir 44 b and then rotated to pull up the second resin composition 12 b with the surface of the coating roll 41 b .
  • an excess portion of the second resin composition 12 b pulled up with the surface of the coating roll 41 b is scraped off using a doctor blade 43 b .
  • the protective sheet 31 is interposed between a pressure roll 42 b and the coating roll 41 b and then pressed against the coating roll 41 a by the pressure roll 42 a so that the second resin composition 12 a is uniformly transferred to the protective sheet 31 .
  • a uniform coating is formed on the surface of the semi-cured layer.
  • the curing unit 45 b is, for example, a unit configured to radiate an ultraviolet ray or infrared ray. If the second resin composition is an ultraviolet-curable resin, the curing unit 45 b may be, for example, a UV radiation unit. If the second resin composition is a thermosetting resin, the curing unit 45 b may be, for example, a dryer (heater).
  • the protective sheet 31 having the recording layer 11 a and the intermediate layer 11 b thereon is transferred to a subsequent process via a transfer roll 45 .
  • the processes from “the first coating process” to “the completely curing process” are repeated multiple times as a subsequent process.
  • multiple recording layers 11 a and multiple intermediate layers 11 b are alternately laminated on the protective sheet 31 , forming a bulk layer 1 on the protective sheet 31 .
  • the final process may be to peel the protective sheet 31 from the bulk layer 1 and then wind the bulk layer 1 and the protective sheet 31 about different rolls.
  • the desired film-shaped bulk layer (a laminate for use in an optical information recording medium) is obtained.
  • FIGS. 14A to 15C there will be described an example of a method for manufacturing an optical information recording medium 10 according to a third embodiment of the present application.
  • a first resin composition 12 a is dropped on the inside radius of a substrate 4 using an applicator 21 a , and the first resin composition 12 a dropped is stretched in the circumferential direction of the substrate 4 by spin coat to form a coating having a uniform thickness on the substrate 4 .
  • the first resin composition 12 a include thermosetting resins and ultraviolet-curable resins.
  • the resin composition that can be used in the present manufacturing method is not limited these and may be an energy beam-curable resin, thermoplastic resin, or the like other than ultraviolet-curable resins.
  • the coating made of the first resin composition 12 a formed on the substrate 4 is cured by radiating an infrared ray or ultraviolet ray from a radiation source 23 a .
  • a recording layer 11 a having a uniform thickness is formed on the substrate 4 .
  • the radiation source 23 a for infrared radiation include IR lamps
  • examples of the radiation source 23 a for ultraviolet radiation include UV lamps.
  • Examples of a UV lamp include high-pressure mercury-vapor lamps and flash UV/H bulbs.
  • an oxide layer having linear absorption characteristics is formed on a surface of the recording layer 11 a by radiating an ultraviolet ray from a radiation source 23 b .
  • the oxide layer has a concentration distribution in which the oxygen concentration continuously decreases from the surface of the layer along the thickness direction.
  • the refractive index of this oxide layer continuously changes in the thickness direction.
  • the radiation source 23 b for ultraviolet ray application include high-pressure mercury-vapor lamps and UV lamps, such as flash UV/H bulbs. Note that the radiation power of the ultraviolet radiation from the radiation source 23 b is set to a value greater than the radiation power of the ultraviolet radiation from the radiation source 23 a.
  • a second resin composition 12 b is dropped on the inside radius of the substrate 4 using an applicator 21 b , and the second resin composition 12 b dropped is stretched in the circumferential direction of the substrate 4 by spin coat to form a coating having a uniform thickness on the recording layer 11 a .
  • the second resin composition 12 b include thermosetting resins and ultraviolet-curable resins.
  • the resin composition that can be used in the present manufacturing method is not limited these and may be an energy beam-curable resin, thermoplastic resin, or the like other than ultraviolet-curable resins.
  • the coating made of the second resin composition 12 b formed on the recording layer 11 a is cured by radiating an infrared ray or ultraviolet ray from a radiation source 23 c .
  • the recording layer 11 a and an intermediate layer 11 b are formed on the substrate 4 .
  • the radiation source 22 c for infrared radiation include IR lamps
  • examples of the radiation source 22 c for ultraviolet radiation include UV lamps.
  • a cover layer 3 having a selection reflective layer 2 thereon is bonded to one principal surface of the bulk layer 1 formed on the substrate 4 .
  • the desired optical information recording medium 10 is obtained.
  • a recording mark is preferably formed on the interface between a recording layer 11 a including the oxide layer, and an intermediate layer 11 b .
  • the reason is that since the oxide layer serves as a light absorption layer, a recording mark is easily formed.
  • a sample having a refractive index that continuously changes in an interface and a sample having a refractive index which discontinuously changes in an interface were prepared, and the amount of reflected light was evaluated.
  • a glass substrate having a diameter of 120 mm and having a center hole having a diameter of 15 mm in the center thereof was prepared as a substrate.
  • an ultraviolet-curable acrylic resin B for recording layer formation was applied onto the glass substrate by spin coat to form a coating having a thickness of about 50 ⁇ m, and then the coating was semi-cured by radiating an ultraviolet ray of 0.37 J/cm 2 thereto.
  • the ultraviolet dose was set to 80% or less of the dose when completely curing the coating.
  • an ultraviolet-curable acrylic resin A for resin thin film formation was applied onto the semi-cured layer by spin coat to form a coating having a thickness of about 2 ⁇ m.
  • the ultraviolet-curable acrylic resin A for resin thin film formation and the semi-cured ultraviolet-curable acrylic resin B for recording layer formation were mutually dissolved on an interface a 2 .
  • the coating formed on the semi-cured layer was cured, and the semi-cured layer was completely cured.
  • a recording layer and a resin thin film were formed on the glass substrate.
  • the materials of the substrate, the recording layer, the resin thin film, and the adhesive layer were selected such that the difference in refractive index between the substrate and the recording layer was 0.05 or less; the difference in refractive index between the recording layer and the resin thin film was 0.1 or more; and the difference in refractive index between the resin thin film and the adhesive layer was 0.2 or more.
  • An optical information recording medium was obtained as in Example 1, except that a recording layer was formed on a glass substrate by applying an ultraviolet-curable acrylic resin B onto the glass substrate to form a coating and then radiating an ultraviolet ray to the coating to completely cure the coating.
  • the amounts of reflected light of the optical information recording media of Example 1 and Comparative Example 1 thus obtained were evaluated as follows. There was monitored the amount of reflected light when the optical information recording medium was rotated while regeneration light was focused on an interface a 1 between the resin thin film A and the adhesive resin layer C. As a result, light amount variations regarded as having been caused by light reflected from the interface a 2 were observed in Comparative Example 1. With respect to the above evaluation, it is believed that light reflected from the interface includes two types of reflected light, that is, light reflected from the interface a 2 between the recording layer B and the resin thin film A and light reflected from the interface a 1 between the resin thin film A and the adhesive resin layer C and that the two types of light reflected from the interfaces have caused the light amount variations.
  • Example 1 On the other hand, almost no light amount variations regarded as having been caused by interference between light reflected from the interfaces were observed in Example 1. The reason seems that while the difference in refractive index between the recording layer and the resin thin film is 0.1 or more in Example 1 as in Comparative Example 1, the refractive index continuously changes in the interface between the recording layer and the resin thin film and thus reflection of regeneration light from the interface between the recording layer and the resin thin film is reduced. Note that the continuous changes in refractive index in the interface between the recording layer and the resin thin film are believed to be made by the mutual dissolution of the materials of the recording layer and the resin thin film in that interface.
  • Samples were prepared while changing the semi-cured state of the recording layer by adjusting the dose (cumulative amount of light), and the reflectance of light reflected from the interface between the recording layer and the resin thin film was evaluated.
  • the refractive indexes n of the recording layer and the resin thin film were adjusted within a range 1.65 to 1.72 and within a range of 1.45 to 1.5, respectively.
  • the ultraviolet dose when forming a semi-cured layer was set to 40% or less of the dose when completely curing a coating. Except for the above conditions, an optical information recording medium was obtained as in Example 1.
  • Example 2-1 Except that the ultraviolet dose when forming a semi-cured layer was set to 60% of the dose when completely curing a coating, an optical information recording medium was obtained as in Example 2-1.
  • Example 2-1 Except that the ultraviolet dose when forming a semi-cured layer was set to 80% or more of the dose when completely curing a coating, an optical information recording medium was obtained as in Example 2-1.
  • Table 1 shows the evaluation results of the optical information recording media of Examples 2-1 to 2-3.
  • Table 1 indicates that adjusting the dose to change the degree of cure of the ultraviolet-curable acrylic resin for recording layer formation causes changes in the reflectance of light reflected from the interface between the recording layer and the resin thin film. The reason seems that the adjustment of the dose caused changes in the mutual dissolution state in the interface and thus changed the refractive index of the interface.
  • the transition region (interface) in which the refractive index continuously changes was modeled using a multilayer film in which the refractive index gradually changes; the number of layers of the multilayer film or the thickness of the multilayer film was changed; and the reflectance and transmittance were obtained through a simulation.
  • the reflectance and transmittance of a laminate was obtained through a simulation as in Test Example 3-1.
  • the reflectance and transmittance of a laminate was obtained through a simulation as in Test Example 3-1.
  • the reflectance and transmittance of a laminate was obtained through a simulation as in Test Example 4-1.
  • the reflectance and transmittance of a laminate was obtained through a simulation as in Test Example 4-1.
  • layers whose refractive index n was 1.69 to 1.41 constitute a multilayer film having a total thickness of 150 nm in which the refractive index n increases by 0.01 for every 5-nm thickness increase.
  • FIGS. 13A to 13D show graphs having a horizontal axis which represents the thickness of the transition region in an interface structure in which the refractive index gradually changes from 1.4 to 1.7 and a vertical axis which represents the reflectance from the interface structure when the incident angle of light having a wavelength of 400 nm was 0°, 15°, 30°, and 45°. Assuming that the refractive index monotonously increases by 0.02 for every one-fifteenth of the thickness of the transition region, calculations were made.
  • FIGS. 13A to 13D indicate that when the incident angle of light was about 30° or less and when the width of the region between a layer whose refractive index n is 1.40 and a layer whose refractive index n is 1.70 (hereafter referred to as “the transition region”) is about 100 nm or more, sufficient reflectance reduction effects can be obtained.
  • the reflectance can be reduced and the transmittance can be increased.
  • the periodicity of the reflectance due to the thickness of the transition region tends to decrease as the number of layers of the transition region increases.
  • a micro-domain structure (a structure including geometrically convoluted micro-regions) may be formed.
  • the micro-domain size in the interface also becomes larger. This may be detected as an optical change, acting as noise.
  • a preferred upper limit of the transition region is about 1 ⁇ m.
  • the structures, methods, processes, shapes, materials, numerical values, and the like used in the embodiments are illustrative only, and structures, methods, processes, shapes, materials, numerical values, and the like different from these may be used as necessary.
  • the number of types of resin layers forming a bulk layer (laminate) is not limited to two, and three or more types of resin layers may be combined to form a bulk layer.
  • the combination of refractive indexes is not limited to the exemplified combination “high-refractive-index layer/low-refractive-index layer . . .
  • high-refractive-index layer/low-refractive-index layer and a modification as described below is also possible: by further incorporating a thin high-refractive-index layer B and a thin low-refractive-index layer B into the multilayer structure, there is made a combination a combination “high-refractive-index layer A/high-refractive-index layer B/low-refractive-index layer A/low-refractive-index layer B/high-refractive-index layer A/high-refractive-index layer B . . .
  • the present application which suppresses interface reflection caused by any interface, is also applicable to a structure in which the periodicity of the multilayer structure is eliminated from the above example.
  • the present application may be configured as follows:
  • An optical information recording medium including a plurality of laminated resin layers, wherein at least one of interfaces between the resin layers has a refractive index which gradually changes in a thickness direction of the resin layers.
  • the optical information recording medium according to (1) wherein the refractive index continuously changes.
  • each of the resin layers contains one of an ultraviolet-curable resin and a thermosetting resin as a main ingredient.
  • a laminate for use in an optical information recording medium including: a plurality of laminated resin layers, wherein interfaces between the resin layers are configured such that a recording mark can be formed thereon, and wherein at least one of the interfaces between the resin layers has a refractive index which gradually changes in a thickness direction of the resin layers.

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US20130128710A1 (en) * 2010-07-13 2013-05-23 Fujifilm Corporation Optical information recording medium
US20130128715A1 (en) * 2010-07-13 2013-05-23 Fujifilm Corporation Optical information recording medium and method for manufacturing same
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US20140029403A1 (en) * 2011-03-28 2014-01-30 Fujifilm Corporation Optical information recording medium and method for recording information in optical information recording medium

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US20130121127A1 (en) * 2010-07-13 2013-05-16 Fujifilm Corporation Optical information recording medium and method for manufacturing same
US20130128710A1 (en) * 2010-07-13 2013-05-23 Fujifilm Corporation Optical information recording medium
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